1. Technical Field of the Invention
The present invention relates to the use of at least one antibody specific for papillary fibroblasts as a marker for the quality of skin, in particular of a skin equivalent.
2. Description of the Prior Art
It is of course well known that human skin consists of two closely linked compartments or strata, namely, the epidermis and the dermis.
The epidermis is principally comprised of three cell types, keratinocytes, which themselves constitute the majority of the cells of the epidermis, melanocytes and Langerhans cells. These cells constitute a keratinized epithelium which is differentiated into superposed layers or strata surmounted by a layer of dead cells forming the stratum corneum.
The dermis provides the epidermis with a solid support. It is also the nourishing element of the epidermis. It principally comprises fibroblasts and an extracellular matrix which is itself principally collagen, elastin and a substance known as “ground substance”. This set of extracellular components is synthesized by the fibroblasts. Leukocytes, mastocytes and tissue macrophages also are present therein. Too, it also comprises blood vessels and nerve fibers. In normal skin, i.e., skin which is neither pathological nor cicatricial, the fibroblasts are in the quiescent state, i.e., non-proliferative, relatively inactive in metabolic terms and immobile.
Indeed, the dermis is subdivided into two regions; firstly, a thin superficial dermis, termed papillary dermis, and secondly, the deep dermis, termed reticular dermis, which constitutes the great majority of the dermis.
The papillary dermis is the part of the dermis which is in contact with the epidermis, and it contains so-called papillary fibroblasts.
The reticular dermis is the region of the dermis which then extends down to the subcutaneous fatty layer, and it contains the reticular fibroblasts. In normal skin, these two regions reflect significant differences. The papillary dermis is metabolically more active than the reticular dermis.
Papillary and reticular fibroblasts in culture exhibit differences in their growth potential. With immunolabelling, it is possible to demonstrate that decorin, small-sized dermatan sulfate proteoglycan (DSPG), is more abundant in the papillary dermis than in the reticular dermis. Papillary fibroblasts secrete up to approximately 6 times more decorin than reticular fibroblasts.
Thus, in normal skin, the dermis comprises of at least two fibroblast populations, which can only have fundamental consequences on the skin itself.
In the domain of skin equivalents (or skin reconstructed in vitro), it is known to prepare dermis equivalents with each of the fibroblast populations isolated beforehand. It is also known to prepare dermis equivalents into which the two populations isolated beforehand are introduced. However, the problem remains of identifying the various fibroblast populations in dermis equivalents reconstructed from a random population of fibroblasts. After establishing in culture the dermis equivalent, does the latter have at least the two fibroblast populations, reticular and papillary, which are present in the dermis of normal skin? Now, it was previously recognized that normal skin has these two populations, and it is understood that skin reconstructed in vitro will be all the more similar to normal skin when it includes at least the two fibroblast populations.
To date, to applicants' knowledge, there exists no simple and effective means, particularly a means which does not impair the skin equivalent, which makes it possible to establish without ambiguity whether reconstructed skin either does or does not contain at least the two papillary and reticular fibroblast populations.